A decorative sheet is a thermoplastic sheet having a decorative image on one surface and an adhesive layer on the other surface and is used for providing decorative images on a surface of an article having a three-dimensional curved surface, such as an outside or inside surface of a building and a vending machine. The decorative sheet is generally adhered on a surface of an article by the following two methods:
(1) A decorative sheet is heated in a place for operation to a given temperature, generally 40 to 60° C. and is adhered on an article under pressuring when the decorative sheet is kept in the given temperature.
(2) A decorative sheet is adhered on an article by a molding method, such as vacuum molding under heating and the like.
Typically, the decorative sheet is made of such a material that either one of the methods or both are applicable. A decorative sheet that has been used for this purpose is usually composed of a vinyl chloride resin as thermoplastic resin sheet. The vinyl chloride resin has good heat moldability and good surface properties, such as wear resistance, chemical resistance and the like. The vinyl chloride resin, however, has recently been avoided and desirously replaced with another resin that can be disposed of without harm or one that can be recycled.
In order to comply with the above requirement, Japanese Kokai Publication No. 48014/1996 proposes a decorative sheet formed from a polyolefin resin, such as polyethylene or polypropylene as thermoplastic resin sheet. Japanese Kokai Publication No. 2000-94596 also proposes a decorative sheet having a protective layer formed from polyester resin thereon.
However, the polyolefin resin disclosed in Japanese Kokai Publication 48014/1996 is crystalline and therefore has a softening temperature too high (more than 100° C.) to conduct a heat adhesion using such a temperature that a handy heating apparatus, such as a dryer can be used in a place for operation.
In addition, the decorative sheet suggested in Japanese Kokai Publication 2000-94596 is designed for the operation (2) mentioned above and therefore is difficult to conduct adhesion in a place of operation by using a handy heating apparatus, such as a dryer. The polyester resin suggested in the this publication has a glass transition temperature of 60 to 85° C. and therefore is not adhered at a temperature less than 60° C. which is generally a heatable temperature by a heating apparatus, such as dryer.